Insulated bus bars and assembly



Aug. 24, 1965 H STANBACK INSULATED BUS BARS AND ASSEMBLY Filed April 2 1963 ZUNSULATING SHEET) MATERml.)

,/QUNSULATING FILM) (ADHESIVE msuLATlNG 13,74 MATERIAL) ./'cuADHEswE INSULATING 3,202,756 INSULATED BUS BARS AND ASSEMRLY Harris I. Stanback, Lexington, Ky., assignor to Square D Company, Park Ridge, Ill., a corporation of Michigan Filed Apr. 2, `1963, Ser. No. 269,970 12 Claims. (Cl. 174-99) This invention relates generally to bus bar assemblies, and more particularly to a method of insulating bus bars in a bus duct structure.

For compactness and low reactance, it is desirable to position the bus bars of a bus duct structure extremely close to each other, but the closer to each other they are arranged, the more diicult it is to adequately electrically insulate them from each other.

An object lof .the present invention is to provide an improved bus duct structure in which the bus bars are arranged closer to each other than formerly.

Another object is to provide improved insulation for vthe bus bars of a bus duct.

A further object is* to provide a compact bus duct structure in which the bus bars are arranged closer to each other than formerly and yet the bus duct has irnproved heat dissipating ability.

A still further object' is to provide an improved method of applying insulation separately to at bus bars of a bus duct, particularly with respect to opposite edge portions of the bus bars.

Yet another `object is to provide the bus bars of a bus duct with insulation equivalent in insulating properties to films of polyester material wrapped completely around the respective bus bars without actually wrapping films of the diicult-to-form polyester material completely around the respective bus bars.

An additional object of the invention is to provide improved double insulation for the bus bars of a bus duct including alternate layers of two dissimilar insulating materials.l

Other objects will appear when the following specification is considered along with the accompanying drawings in which:

FIGURE 1 is a perspective view of a portion of a bus duct structure constructed in accordance with this invention, parts thereof being progressively cut away lengthwise of the bus bars to better illustrate the insulation arrangement of the busbar assembly;

FIGURE 2 is a Vfragmentary broken cross sectional view of a layer ofiinsulation before itis applied to a bus bar in accordance'with this invention;

FIGURE 3 is a cross sectional view of a bus bar having insulation applied thereto in accordance with this invention;

FIGURE4 is a cross sectional view of a bus bar having insulation applied thereto in an alternate manner in accordance with this invention; and

FIGURE 5 is a fragmentary edge view of a bus bar assembly constructed in accordance with this invention.

In FIGURE 2 a fragmentary broken cross ysectional View of a strip 12 of adhesive varnished glass cloth is shown and may be thought of as extending lengthwise perpendicularly to the plane of the paper. A pair of parallel spaced strips 14 of polyester film, a strong and durable material having a relatively high dielectric strength and through which heat can be directly dissipated without substantially reducing the dielectric strength, are placed in position on the adhesive side of the strip 12 of varnished glass cloth.

The strip 12 with the two polyester lm strips 14 thereon is applied to and wrapped substantially once around a flat bus bar as shown on a bus bar 15 in FIG- URE 3 and on a bus bar 17 in FIGURE 4, the strips United States Patent O M zio 3,202,756 Patented Aug. 24, 1965 14 respectively being formed substantially symmetrically around the opposite edge portions of the bus bar and the width of the strip 12 being such that a small gap 16 occurs between the opposite edges of the strip 12. Preferably a second strip 12a of adhesive varnished glass cloth with two parallel spaced strips 14a of polyester film thereon is then applied to and wrapped substantially once around the bus bar over the first strip 12, the strips 14a also respectively being formed substantially symmetrically around the opposite edge portions of the bus bar over the strip 12 and strips 14 and the Width of the strip 12a being such that a small gap 16a occurs between the opposite edges of the strip 12a. The strips 12 and 12a may be applied from opposite sides of the bus bar, as shown on the bus bar 15 in FIGURE 3, or they may be applied from the same yside of the bus bar, as shown on the bus bar 17 in FIGURE 4. The spacing of the strips 14a with respect to the opposite edges of a strip 12a is different from the spacing of the strips 14 with respect to the opposite edges of a strip 12, and thus the gaps 16 and 16a are spaced apart so as not to be aligned on the bus bar 17.

An exemplary bus bar assembly 18 using two of the insulated bus bars 17 and one of the insulated bus bars 15 is shown in FIGURES 1 and 5. Sheets of insulation 2t), preferably of polyester material, are placed respectively between the bus bars and on the outer sides of the outer bus bars. The opposite edge portions of the sheets of insulation 2t) overlap the strips 14 and 14a, thus providing insulation equivalent to films of polyester material wrapped completely around the respective bus bars. The individually wrapped bus bars and sheets of insulation 29 together are helically wound with epoxy impregnated glass cloth 21 to form the bus bar assembly 18. The bus bar assembly may then be adhesively secured within a housing 22 in intimate contact with the inner surfaces of one pair of opposed sidewall portions and in `spaced relation to a second pair of opposed side- Wall portions of the housing, as shown in FIGURES l and 5.

The gaps 16 and 16a are provided to eliminate overlapping of the opposite edges of the respective strips 12 and 12a. High spots are thus prevented and the wrappped bus bars 15 and 17 may be placed in intimate contact with the polyester sheets 20', air being entrapped substantially only at the gaps 16 and 16a. Good heat transfer to the housing 22 is thus assured. It should be noted that a large amount of air appears to be entrapped between the sheets 2t) and the wrapped bus bar 17 in FIGURE 4. This is not so in an actual bus bar assembly constructed in accordance with the invention, but only appears so due to limitations of drawing. In actual practice, the strips of polyester film 14 and 14a may be as thin as two thousandths of an inch, the strips of varnished glass cloth 12 and 12a may be as thin as one hundredth of an inch, and the polyester sheets 29 may be as thin as one hundredth of an inch.

In the wrapping of' the individual bus bars, adhesive could be applied to the polyester film strips 14 and 14a and the strips 14 and 14a could be applied separately to the bus bars. However, the strips 14 and 14a are preferably first applied to the strips 12 and 12a, respectively, in the manner described, and the strips 12 and 12a with the strips 14 and 14a thereon then applied to the bus bars.

It will thus be seen that an extremely compact bus bar assembly having low reactance, adequate electrical insulation, and low heat rise characteristics has been provided. Various modifications may be Imade in `the structure and method of `construction disclosed Without departing from the spirit and scope of the invention.

I claim: V 1. An individually wrapped bus 'bar for use in ain assembly of bus bars, comprising (a) a flat elongated bus bar,

(b) a pair of elongated non-self-conforming strips of insulating film wrapped respectively over opposite longitudinal edge faces of said Ibus bar and the portions on opposite sides thereof adjacent ysaid longitudinal edge faces, and

(c) an elongated "stripV of adhesive insulating material of a width approximately equal to but no greater than the periphery of said bus bar, said strip of adhesive insulating material being wrapped only once substantia'lly around said bus bar and the strips of insulating `film thereon and conforming said strips of insulating film to said bus bar. p,

2. An individually wrapped bus ybar Ias claimed in claim 1, wherein said insulating lrn strips are formed of a polyester mater-ial. I

V1i. An individually wrapped bus 'bar as clalmed 1n clalrn 1, wherein said strip of adhesive insulating material 1s formed of varnished glass cloth. 4. An individually wrapped bus lfor use in an assembly yof bus bars, comprising (a) a iiat elongated bus bar,

(b) a Vfirst pair of elongated nonselfconforming strips ing said first pair of insulating iilm strips to said a second pair of elongated non-self conforming greater than the periphery of said bus bar, said second strip of adhesive insulating material being wrapped only once substantially around said bus bar over said iirst strip of adhesive insulating material and said rst and second pairs of insulating iilm strips and conforming said second pair of insulating film strips to said bus bar.

5. An individually wrapped bus bar as claimed in claim 4, wherein said insulating film strips formed of a polyester material.v

6. An assembly of bus bars comprising V(a) a plunality of flat elongated bus bars in flatwise `stacked relationship, Y

(b) a plurality of pairs of elongated non-self-conforrning strips yof insulating lil-m, each of said bus bars having a pair of said insulating film strips wrapped respectively over opposite longitudinal edge faces of lthe bus bar and 'the portions on opposite sides thereof adjacent said longitudinal edge faces,

1 (c) a plurality of elongated strips of adhasive insulating material wrapped respectively only `once substantially around said bus bars and the pairs of in- -sulating iilrn strips thereon and conforming said pairs v of insulating film strips respectively to said 'bus bars,

and

(d) a plurality ofV elongated insulating sheets respectively between adjacent bus bars'and on the outer sides of the two outer bus bars vin overlapping relationship with 4said insulating film strips.

7. An assembly of bus bars as claimed in claim 6, wherein said strips of adhesive insulating material are formed of varnished glass cloth.

8. An assembly of bus bars as. claimed in claim 6, wherein lsaid insulating film strips are formed of a polyester material. V

9. An assembly of bus bars as .claimed in claiml 6, wherein said insulatingY s'heets are formed of a polyester material. y

10. An assembly of lbus bars as claimed in Vclaim 6, including a liexible insulating material wrapped helically arroundY said Wrapped bus bars and insulating sheets collectively.

11. An assembly -of bus bars as claimed in claim 10, wherein said iiexible insulating material Wrapped helically around` said wrapped bus bars and insulating sheets collectively is formed of epoxy impregnated glass cloth.

12. A bus ductL including an assembly of bus bars as claimed in claim `10, and an elongated hollow housing therefor, said housing having a rectangular -aperture extending therethrough, an'd said assembly of bus bars being disposed in said rectangular aperture in contact flatwise of said bus bars with the inner surfaces of a lirst pair of opposed sidewall portions of said housing and spaced edgewise of said bus .bars from a second pair of opposed sidewall portions of said housing. y

'Y References Cited by the Examiner Y OTHER REFERENCES German printed application 1,128,900, May 3, 1962. Starr Corona Properties of Insul-ating Materials, Electrical Engineering, I une 1956, Table lII.

' L'ARAMIE E.'ASKIN, Primary Examiner.

YJOHN P, WILDMAN, JOHN F. BURNS, Examiners. 

1. AN INDIVIDUALLY WRAPPED BUS BAR FOR USE IN AN ASSEMBLY OF BUS BARS, COMPRISING (A) A FLAT ELONGATED BUS BAR, (B) A PAIR OF ELONGATED NON-SELF-CONFORMING STRIPS OF INSULATING FILM WRAPPED RESPECTIVELY OVER OPPOSITE LONGITUDINAL EDGE FACES OF SAID BUS BAR AND THE PORTIONS ON OPPOSITE SIDES THEREOF ADJACENT SAID LONGITUDINAL EDGE FACES, AND (C) AN ELONGATED STRIP OF ADHESIVE INSULATING MATERIAL OF A WIDTH APPROXIMATELY EQUAL TO BUT NO GREATER THAN THE PERIPHERY OF SAID BUS BAR, SAID STRIP OF ADHESIVE INSULATING MATERIAL BEING WRAPPED ONLY ONCE SUBSTANTIALLY AROUND SAID BUS BAR AND THE STRIPS OF INSULATING FILM THEREON AND CONFORNING SAID STRIPS OF INSULATING FILM TO SAID BUS BAR. 